The invention relates in general to testing the functioning of radio apparatuses. In particular the invention relates to testing the functioning of data channels in a radio apparatus. The description of the invention especially focuses on the type approval testing of the functioning of a radio apparatus but the functioning of radio apparatuses is of course tested in many other connections as well, e.g. during product development, manufacture, repair and service.
Up till the second-generation digital cellular radio systems, mobile stations have been mainly telephones and the information transmitted has been first analogue speech and then digitized speech. A certain so-called traffic channel has been specified for speech transmission on a radio connection between mobile station and base station, and the characteristics of said traffic channel have been optimized according to features typical of digitized speech. However, the use of mobile stations is becoming more diversified as extensions are being planned to the second-generation systems and especially when the third-generation cellular radio systems will be introduced. Good examples of second-generation extensions are the systems that are planned as GSM (Global System for Mobile telecommunications) extensions, namely, HSCSD (High Speed Circuit Switched Data), in which multiple timeslots in a TDMA frame are allocated to a connection between a terminal and base station, GPRS (General Packet Radio System), which is based on packet switched connections between a base station and terminal instead of the circuit switched connections used earlier, and EDGE (Enhanced Data rates for GSM Evolution), which achieves a considerably higher momentary transmission rate between a base station and terminal than prior-art systems by changing the modulation methods and channel coding. GSM generally refers to all its different versions at the 900-MHz, 1800-MHz, and 1900-MHz operating frequencies, although the latter two have also been called DCS1800 and DCS1900 (Digital Communications System at 1800/1900 MHz).
In the more diversified mobile communications, data transmission will have much more importance than nowadays. Data generally refers to transmitted information other than digitized speech. Data transmission is characterized by generally not being real-time and having totally different requirements concerning error correction and transmission rate fluctuations than digitized speech. Data transmission is used especially when a terminal of a cellular radio system comprises a mobile station to which a separate data-processing auxiliary such as a computer is connected. For data transmission, mobile communication systems specify special data channels the characteristics of which can be optimized for data transmission.
Testing data channel related functions of terminal equipment has proven problematic. Data channels have traditionally been used in situations according to FIG. 1 where a separate data terminal equipment (DTE) is locally connected to a mobile station (MS) functioning as terminal equipment through a terminal adapter (TA). During the test, a simulation system (SS) simulates a cellular radio system. Testing the functioning of a data channel has required that between the SS and DTE a working data link is established via the MS, serving a simultaneously running application requiring data transmission. The application in question has to be active in the DTE and it has to be simulated in the SS, which results in extra complexity in the test. Furthermore, GSM specification 05.05 specifies quite a high coding gain for data channels with respect to channel coding, which means that the number of bits to be tested easily grows quite large. This, in turn, adds to the duration of the test.
The need for a separate data terminal equipment and an application running in it as well as the long testing time easily result in that the data terminal equipment drops the data connection established for the test because a time-out occurs in the application in question or because the number of errors observed on the data channel exceeds a threshold specified in the application. In addition, the general test practice of looping a frame received by the data terminal equipment in the downlink direction from the SS bit by bit back to the SS in the uplink direction usually confuses the uplink frame numbering typical of data channels, which also causes the data terminal equipment to disconnect the data call. Furthermore, problems arise from the fact that information transmitted on data channels may comprise higher-level units which have to be broken down to several consecutive or closely-situated bursts for the radio connection between base station and mobile station. To be able to ensure error-free reception of information thus transmitted a data terminal equipment must decode a large number of frames and recombine the data in them. All this leads to that the testing of the functioning of a data channel according to the traditional method tests largely the operation of the terminal adapter and data terminal equipment connected to the mobile station rather than the operation of the mobile station itself. This is inappropriate, particularly as concerns tests related to type approval of mobile stations.
Solutions for the disconnection problem have been searched for in the direction of DTE operation, i.e. a special test mode has been specified in which normal responses to a long connection time and confusion of frame numbering are left out. This, however, will not eliminate the problem that the result of the test intended to test the mobile station largely depends on whether the data terminal equipment and the software controlling its operation function correctly.
An object of the present invention is to provide a method for testing the functioning of data channels in a mobile station such that the testing is directed as intended to the operation of the mobile station. Another object of the invention is to provide a mobile station in which the operation of data channels can be tested in the above-mentioned manner.
The objects of the invention are achieved by specifying the necessary functions to loop the downlink data related to the data channels tested back in the uplink direction in a mobile station such that the data do not travel through external data terminal equipment.
The method according to tie invention is characterized in that in response to a command of a certain protocol level received from the test equipment the mobile station establishes a data channel test loop to loop the downlink data received from the test equipment back in the uplink direction to the test equipment, and during the test, the reception of downlink data and transmission of uplink data are carried out controlled by said protocol level.
The invention is also directed to a mobile station which is characterized in that it comprises means for cycling downlink data received from test equipment back in the uplink direction to the test equipment in response to a command of a certain protocol level, controlled by said protocol level.
In accordance with the invention, the communications protocol controlling the test situation is altered such that in the test mode, only the necessary lower protocol level connection is opened between the mobile station and the test equipment simulating the cellular radio system. There is no need to connect an external data terminal equipment to the mobile station, nor is it necessary to establish a data connection proper in the sense that the higher protocol levels were aware of the connection established. As the higher protocol levels are not aware of any data connection, no function related to them will drop the connection prematurely. Test data are transferred downlink from the test equipment to the mobile station which loops the appropriate test data back in the uplink direction.
To test various functions of a mobile station a plurality of embodiments of the invention can be disclosed which differ in how xe2x80x9cdeepxe2x80x9d in the mobile station the looping back of test data in the uplink direction occurs. Depth refers to the number of components and/or functions the downlink test data passes in the mobile station before being looped back uplink. Preferred embodiments include e.g. the loopback of test data, after reception, demodulation, and decryption to encryption, modulation and transmission, and after reception, demodulation, decryption and channel decoding to channel encoding, encryption, modulation and transmission.
The invention makes it possible to direct the testing of data channel functionality to those mobile station parts the operation of which is to be verified e.g. in connection with mobile station type approval tests. Furthermore, test equipment can be made simpler and tests avoid the difficulties caused by the operation of data terminal equipment. It is a further advantage of the invention that the connection between the test equipment and the mobile station tested will not be disconnected in the middle of a test. An additional advantage of the invention is that testing methods used by different manufacturers will become more uniform, which improves the reliability of testing.